In lighter than air vehicles, such as the vehicle 1 shown in FIG. 1, temperature and pressure changes resulting from altitude changes and varying atmospheric conditions may cause lift gas inside a hull of the vehicle 1 to expand or contract, resulting in a constantly varying volume of lift gas. To maintain a constant internal pressure, such vehicles may have one or more ballonets (not shown) within the hull 2. The ballonets may react to changes in volume by passively discharging air to or accepting air from the atmosphere, to maintain hull pressure within acceptable limits, to maintain hull shape. Additionally, the vehicle 1 may have ballast, in order to manage the large buoyancy difference between the launch and operational elevations. In high-altitude vehicles, fully inflated at launch, large ballast loads may be required. The ballast (such as fluid or sand) may be stored in a hopper 3 and a release mechanism may allow the ballast to be drained or jettisoned from the hopper during assent as needed. However, such configuration may impart large local loading at the attachment side, and therefore a large scar (i.e., drag-inducing) support structure to distribute the load into the hull 2 may be required. The supporting structure, hopper 3, and ballast release mechanism remain permanently affixed to the hull 2 after the ballast is jettisoned, imparting a large scar mass, adversely affecting performance. Additionally, due to the external location of the system, increased drag may result throughout the flight, even after the ballast has been drained from the hopper 3. High altitude flight may require larger hoppers, resulting in further loss of efficiency.